1. Field of the Invention
The invention relates to an apparatus for assembling warps of spun fibers and/or filament yarns present in yarn beams to form a textile warp located in a warp beam. The apparatus comprises a pneumatic pressure regulator, an electromagnetically operable pneumatic valve downstream of the pressure regulator, a three-position rotary disk valve downstream of the pneumatic valve, and pneumatically operable yarn beam brake cylinders downstream of the three-position rotary disk valve and connected in parallel with it.
In known assembly systems the warp beam is driven, but the yarn beams are not driven. In the normal operation of the known assembly systems, in order to obtain a constant tension of the yarns between the yarn beams and the warp beam, the non-driven yarn beams are slightly decelerated, that is the available compressed air is reduced by means of a pneumatic pressure regulator to a predetermined lower desired value and is conducted by an electromagnetically operable pneumatic valve downstream of the pressure regulator to a three-position rotary disk valve which is arranged downstream of the pneumatic valve and thence to the yarn beam brake cylinders connected in parallel following the three-position rotary disk valve.
In case of rapid braking of the known assembly systems, caused by a disturbance, for example a thread rupture, the warp beam is braked very quickly, while the yarn beams are usually braked only with some delay.
For rapid braking, the electromagnetically operable pneumatic valve is reversed, so that the air stream coming from the pressure regulator is interrupted and the available compressed air at a higher pressure passes through this pneumatic valve to the following three-position rotary disk valve. However, if this rotary disk valve is closed on the inlet side, it takes a while for it to get into open position. In this case, the compressed air at a higher pressure reaches the brake cylinders of the yarn beam brakes with a delay.
2. Description of the Prior Art
For this reason, the braking of the yarn beams and of the warp beam is not synchronous. The result is that the yarn beams lag, especially if they are still quite full and, therefore, heavy. Due to this fact, the yarns first become very slack and strike against one another, leading to filament ruptures. Thereafter, the yarns are tensioned abruptly, because after the three-position rotary disk valve is switched, the compressed air at a higher pressure suddenly acts on the brake cylinders of the yarn beam brakes. The abrupt tensioning of the yarns may lead to yarn ruptures.